This invention relates to the field of closure and sealing devices, and in particular to an improved closure and sealing device for open-mouthed vessels such as bottles.
The bottled water industry is a major user of closure devices, for example bottle caps on 5-gallon bottles. These caps must of necessity be inexpensive to manufacture, as well as easy to place on the bottle and to remove. A desirable characteristic of bottle caps with which the present invention is particularly concerned is the prevention of the transfer of gas and liquid between the inside of the bottle and the atmosphere. If water escapes from the bottle during storage, then the consumers will become dissatisfied. Conversely, since a prime reason for purchasing bottled water is its purity, it is of the utmost importance that the bottle cap seal the bottle against contamination from the atmosphere. Maintaining a pure and full bottle of water becomes especially difficult because the bottles may undergo substantial shipping and storage and a corresponding variety of temperature and pressure conditions before the water is finally consumed.
A number of bottle caps have been employed in an effort to provide adequate sealing properties. The bottles commonly have a neck having an orifice surrounded by a protruding annular lip and a second annular protrusion on the exterior surface of the neck below the lip. Originally a cork and wax paper were inserted into the orifice and the excess waxpaper was wrapped over the orifice lip and held in position by a rubber band around the neck between the lip and the protrusion. Although seals and caps have become more sophisticated, water bottles tend to retain a neck configuration having an annularly protruding orifice-defining lip and a second annular neck protrusion as employed with cork and paper seals.
With the advent of plastic, various plastic cap designs were offered to seal water bottles and the like. In one such design, as disclosed in Faulstich, U.S. Pat. No. 3,066,820, a plastic cap fit over and around the protruding lip and in addition a central cylindrical appendage which was slightly smaller than the orifice was inserted into the orifice to seal against an inside surface of the bottle neck.
Other plastic cap designs were generally cup-shaped and fit over the bottle neck covering the protruding lip and a portion of the annular protrusion. Such a cap is shown in Faulstich, U.S. Pat. No. 3,392,862.
Two shortcomings of these designs were the difficulty with which they could be removed from the bottle and their sealing qualities were not as effective as they might be. One solution to the first shortcoming offered in some commercially available caps was to mold a groove in the interior surface of the cap and to provide a tab depending from a lower edge of the cap and adjacent said groove. The cap could then be removed by lifting on the tab and tearing the cap. While this design ameliorates one shortcoming, it aggravates the other because the formation of a groove on the interior surface of the cap interferred with the formation of a seal between the cap and the bottle neck. Faulstich U.S. Pat. No. 3,392,862 shows a groove which has part of its length molded in the exterior surface of the cap in the region near the annular protrusion of the bottle neck, but which has the rest of its length molded in the interior surface of said cap which partially cures this shortcoming.
The second shortcoming, which has affected all caps, is how effectively to seal the bottle against content loss or contamination. One commercially available cap has two tiny annular beads molded on the interior of the cap which are designed to fit against the top surface of the neck lip. These beads are relatively tiny, i.e., they protrude on the order of 0.010" from the interior surface of the cap. The size and the shape of these beads dictates that the seal formed between the cap and the vessel neck surface is essentially point-to-point and the beads are not of sufficient length to form a surface-to-surface contact with the bottle lip so that sealing contact can be maintained even when the cap and neck deform to some extent because of thermal expansion and contraction and manufacturing variances. These beads thus form an ineffective seal, especially when either the cap or bottle neck has molded imperfections or when the plastic cap is deformed by, for example, temperature changes or pressure gradients across a cap/neck seal. Under any of the above conditions the cap beads may fail to contact the lip surface at some points, thereby breaking the seal.